Nonstop forwarding for routed multicast traffic

Abstract

A programmed network device and corresponding method are provided for rebuilding a multicast state upon experiencing a failure in a network using a protocol independent multicast (PIM) protocol. The method includes receiving updates to an outgoing list (Olist) for a given multicast route (mroute) at the network component and updating a PIM cache Olist in the network component with the received updates. During a state of recovering from the failure, the method includes determining whether the PIM cache Olist matches a centralized database Olist located in a centralized database. When a match is found, the method includes publishing an mroute state from the PIM cache to the centralized database.

What is claimed is: 
     
       1. A networking component comprising:
 switching hardware; 
 a centralized database that is used to program the switching hardware; and 
 a protocol independent multicast (PIM) module comprising processing circuitry programmed to create and maintain a PIM cache and to, upon experiencing a failure in a network using a PIM protocol:
 compare an outgoing list (Olist) for a multicast route (mroute) in the PIM cache to an Olist in the centralized database; 
 determine whether the Olist in the PIM cache matches the Olist in the centralized database; 
 publish an mroute state of the mroute from the PIM cache to the centralized database on a condition that the Olist in the PIM cache matches the Olist in the centralized database; and 
 refrain from publishing the mroute state of the mroute from the PIM cache to the centralized database on a condition that the Olist in the PIM cache does not match the Olist in the centralized database. 
 
 
     
     
       2. The networking component of  claim 1 , wherein the processing circuitry receives a PIM message related to the mroute from a neighboring network component. 
     
     
       3. The networking component of  claim 2 , wherein the processing circuitry is configured to updates the Olist in the PIM cache in response to receiving the PIM message. 
     
     
       4. The networking component of  claim 1 , wherein the processing circuitry is configured to, in response to determining that the Olist in the PIM cache does not match the Olist in the centralized database, and detects whether a new interface is present in the Olist in the PIM cache. 
     
     
       5. The networking component of  claim 4 , wherein the processing circuitry is configured to, in response to detecting a new interface is present in the Olist in the PIM cache, adds the new interface to Olist in the centralized database. 
     
     
       6. The networking component of  claim 5 , wherein adding the new interface to the Olist in the centralized database occurs without publishing the mroute state from the PIM cache to the centralized database. 
     
     
       7. The networking component of  claim 6 , wherein the processing circuitry further receives at least one further update to the Olist for the mroute and storing the further update in the PIM cache Olist. 
     
     
       8. The networking component of  claim 1 , wherein the processing circuitry is configured to compute a hash of the Olist in the PIM cache and compute a hash of the Olist in the centralized database. 
     
     
       9. The networking component of  claim 8 , wherein the processing circuitry is configured to compare the Olist in the PIM cache to the Olist in the centralized database by comparing the hash of the Olist in the PIM cache with the hash of the Olist in the centralized database. 
     
     
       10. The networking component of  claim 9 , wherein the processing circuitry is configured to publish the mroute state from the PIM cache to the centralized database when the hash of the Olist in the PIM cache is equal to the hash of the Olist in the centralized database. 
     
     
       11. The networking component of  claim 1 , wherein the processing circuitry is configured to reset a failure recovery status to false upon publishing the mroute state to the centralized database. 
     
     
       12. A method comprising:
 experiencing a failure in a network using a protocol independent multicast (PIM) protocol during a state of recovering from the failure, using at least one processor to:
 receive a PIM message related to a given multicast route (mroute) at a network component; 
 update, based on the received PIM message, an outgoing list (Olist) for the given mroute in the PIM cache (PIM cache Olist) stored in a PIM cache of the network component; 
 determine whether the PIM cache Olist matches a centralized database Olist located in a centralized database; and 
 publish an mroute state from the PIM cache to the centralized database only on condition of the PIM cache Olist matching the centralized database Olist. 
 
 
     
     
       13. The method of  claim 12 , comprising, during the state of recovering from the failure, using the at least one processor to determine that the PIM cache Olist does not match the centralized database Olist and refraining from publishing the mroute state in the PIM cache to the centralized database. 
     
     
       14. The method of  claim 13 , comprising, during the state of recovering from the failure using the at least one processor to detect a new interface in the PIM cache Olist. 
     
     
       15. The method of  claim 14 , comprising using the at least one processor to add the new interface from the PIM cache Olist to the centralized database Olist. 
     
     
       16. The method of  claim 12 , comprising using the at least one processor to compute a hash of the PIM cache Olist, compute a hash of the centralized database Olist, and compare the hash of the PIM cache Olist with the hash of the centralized database Olist in order to determine if the PIM cache Olist matches the centralized database Olist. 
     
     
       17. The method of  claim 16 , comprising, during the state of recovering from the failure, using the at least one processor to publish the mroute state from the PIM cache to the centralized database when the hash of the PIM cache is equal to the hash of the centralized database. 
     
     
       18. A non-transitory computer-readable medium storing instructions executable by a processor to cause the processor to:
 detect that a failure has occurred at a network component and cause the network component to enter a failure recovery state, the network component using a protocol independent multicast (PIM) protocol; 
 during the failure recovery state:
 receive updates to an outgoing list (Olist) for a given multicast route (mroute) at the network component; 
 update a PIM cache Olist in the network component with the received updates; 
 determine whether the PIM cache Olist matches a centralized database Olist located in a centralized database; and 
 publish an mroute state from the PIM cache to the centralized database only on condition of the PIM cache Olist matching a centralized database Olist. 
 
 
     
     
       19. The non-transitory computer-readable medium of  claim 18 , wherein the instructions cause the processor to, in response to determining that the PIM cache Olist does not match the centralized database Olist, refrain from publishing the mroute state in the PIM cache to the centralized database. 
     
     
       20. The non-transitory computer-readable medium of  claim 19 , wherein the instructions cause the processor to, in response to detecting a new interface in the PIM cache Olist, add the new interface from the PIM cache Olist to the centralized database Olist without publishing the mroute state in the PIM cache to the centralized database.